Prestashop modifications

Hello, For our site which we are preparing to be in Prestahop we need some modifications done. Installation is already done and the theme is also already working. We need the following modifications to be done: SHIPPING Standard in Prestashop you van only assign shipping by weight or by the amount of the order. This is not good enough for us. What we want is following: If orders weigh over 451 grams and are below a specific total order amount, we need to be able to set the shipping costs to say cost X. If orders weigh over 451 grams and are above a specific total order amount, we need to be able to set the shipping costs to say cost Y. So we need a combination of shippig costs calculated over weight and total order amount VOUCHERS We want some extra options with vouchers / cart rules / shop rules. - Vouchers that are created for customers, i.e. 10% voucher for the whole shop, must be excluded for use on SALE products or actions - Vouchers that are created for customers, i.e. € 25,00 voucher for the whole shop, must be excluded for use on SALE products or actions MAIL OPTIONS We want more options for the mail than what it is now: Order mails must be sent from no-reply@... Order mails must be sent to sales@ All other mails must be sent from info@ All contact mails must be sent to customerservice@ RETURN OPTIONS We need to be able to choose from diverse options of RMA numbers to be created when a customer wants to sent products back: BNV-RMA_# for returning an article because of reason 1 PFL-RMA_# for returning an article because of reason 2 BND-RMA_# for returning an article because of reason 2 # stands for the number that is assigned to the return shipment, this needs to be auto-increment. PRODUCT PRICING We need to be able to set a 'from' option to the price of products (in Dutch we set it to v.a.). This needs to be created as an extra option in the price section when creating a product and needs to be shown on the product listing page. We need that because some attributes of products rise in price and we want the customers to know that the price then is 'from' a specific amount. CSS CROSS BROWSER FIXING We need the CSS of the template to be fixed for all browsers, we've tried to do this ourselves but we're not capable of getting this done. Please only react if you think youre capable of doing this and will complete this project. After the project is fullfilled I want all the coding that is done to be explained in documents to me, because now and then we need to change some things and I don't want to mess things up... Kind regards, Marco